The present invention relates to a glass spacer for an electron-beam emitting display device and an electron-beam emitting display device with the glass spacer. More particularly, the present invention relates to the glass spacer for an electron-beam emitting display device composed of non alkaline glass which is substantially free of alkali and has about the same linear expansion coefficient as that of soda-lime-silica glass and it also relates to the electron-beam emitting display device with the glass spacer.
The electron-beam emitting display of a light self-emitting type has been served widely as the display of a flat type which provides brighter images and wider angles of view than those of liquid-crystal display devices. The electron-beam emitting display of the light self-emitting type directs electron-beams generated by electron-beam generators at fluorescent members so that the fluorescent members emit fluorescence to form images.
Since the electron-beam emitting display of the flat type forms images by directing electron beams at fluorescent members, components of the display including the electron-beam generators and the fluorescent members are installed in a vacuum container having the internal pressure of 10xe2x88x923 Pa or less. Japanese patent publication H7-230776A discloses a vacuum container having resistance to the atmospheric pressure as shown in FIG. 1.
FIG. 1 shows an exploded perspective view of the electron-beam emitting display of a flat type. The display has a front panel 1 which is composed of a glass panel 15 and an image-forming member 5 which is formed on the internal surface of the glass panel 15, and also a back panel 2 carrying a group of electron-emitting elements which will be described later. The image-forming member 5 includes a fluorescent member which emits light when irradiated with an electron beam generated from the electron-emitting elements. The front panel 1 and the back panel 2 are hermetically connected in such a manner that a supporting core frame 3 is interposed in between the panels 1 and 2 as shown in FIG. 2 which illustrates the section of the display along 2xe2x80x942 line of FIG. 1, and thus the panels 1, 2 and the flame 3 compose a hermetical structure having resistance to atmospheric pressure. Glass spacers 4 are inserted in between the front panel 1 and the back panel 2 to support the panels 1 and 2 against the atmospheric pressure.
The back panel 2 has a glass base 21, element portions 23 composed of Ni, which have a thickness of 100 nm and are disposed on the glass base 21 in a matrix-like arrangement, and wiring portions 24 composed of Ag, which have a thickness of 2 xcexcm and are formed on the glass base 21 so as to supply electricity to the element portions 23. Each of the element portions 23 has an electron-emitting element 25. The wiring portions 24 are arranged in parallel with each other and each pair of the adjacent wiring portions 24 simultaneously supplies electricity to the plural electron-emitting elements 25 which exist along the pair. And furthermore, modulating electrodes, not shown in FIG. 1, each of which includes an electron-passing hole having a diameter of 50 xcexcm, are disposed 10 xcexcm above the glass base 21 with insulation layers of SiO2 interposed between the electrodes and the glass base 21 respectively.
At the surface of the back panel 2, each of the glass spacers 4 is in contact with the top of the wiring portion 24 which exists between a pair of adjacent lines of the electron-emitting elements 25, and at the surface of the front panel 1. Each glass spacer 4 is in contact with one of black stripes where the fluorescent member of the image forming member 15 is not to be irradiated with electrons emitted by the electron-emitting elements 25.
Japanese patent publication H12-203857A describes a method of producing glass spacers for an electron-beam emitting display device with high accuracy, wherein a base glass material having a sectional shape of a close analogy to the desired shape of that of the glass spacers is prepared, the base glass material is heated to have a viscosity of 105 to 109 poise, and the glass material is drawn to form the glass spacer.
According to this method, it becomes easy to form the glass spacers in the desired shape as the analogy in the shape of the section between the base glass material and the drawn base glass material is improved.
In the above Japanese patent publication H12-203857A, such glass composition as shown in the following Table 1 is employed to compose the glass spacers.
The front panel and the back panel of the display normally are composed of soda-lime-silica glass.
As shown in FIGS. 1 and 2, the glass spacers are interposed in between the front panel and the back panel of the vacuum container having resistance to the atmospheric pressure so as to keep the spacing between the panels constant. However, since the glass spacers are exposed to the electron-emitting elements, there can arise such a problem that movable ions such as Na included in the glass of the spacer are unevenly distributed under the influence of bias voltage and, thus, cause the breakage of the electric field. Therefore, the glass spacers are desirable to be composed of non alkaline glass composition in order to prevent the above problem. However, the glass spacers are, on the other hand, desirable to have the same linear expansion coefficient as that of the soda-lime-silica glass which constitutes the front and back panels because the glass spacers are fixed to the back panel of the electron-beam emitting display device by fusion welding at a temperature of about 500xc2x0 C. or lower with using a low-melting glass frit.
The non alkaline glass composition employed in the Japanese patent publication H12-203857A is not suitable for the glass spacers for the electron-beam emitting display device because its linear expansion coefficient is 35 to 40xc3x9710xe2x88x927/xc2x0 C. and differs far from that of the soda-lime-silica glass.
It is an object of the present invention to solve conventional problems as mentioned above and to provide a glass spacer for an electron-beam emitting display device which is composed of non alkaline glass having almost the same linear expansion coefficient as the soda-lime-silica glass, and also provide an electron-beam emitting display device equipped with the glass spacer.
The glass spacer for an electron-beam emitting display device of the present invention is composed of non alkaline glass which is substantially free of alkaline metals and includes SiO2 of 10 to 35 percent by mass, RO, in which xe2x80x9cRxe2x80x9d refers to an alkaline earth metal, of 20 to 60 percent by mass, B2O3 of 9 to 30 percent by mass and Al2O3 of 0 to 10 percent by mass, and the linear expansion coefficient of which is 76xc3x9710xe2x88x927 to 92xc3x9710xe2x88x927/xc2x0 C.
The glass spacer composed of the non alkaline glass which is substantially free of alkali does not cause the electric field breakage arisen from the alkali. The glass spacer is not fractured due to the difference of thermal expansion between the glass spacer itself and the soda-lime-silica glass because the linear expansion coefficient of the non alkaline glass is 76xc3x9710xe2x88x927 to 96xc3x9710xe2x88x927/xc2x0 C. and is approximately equal to that of the soda-lime-silica glass.
In the present invention, the non alkaline glass which constitutes the glass spacer is preferable to have a linear expansion coefficient particularly of 78xc3x9710xe2x88x927 to 88xc3x9710xe2x88x927/xc2x0 C.
The non alkaline glass may further include La2O3 of 0 to 30 percent by mass, ZnO of 0 to 8 percent by mass and TiO2 of 0 to 5 percent by mass.
The electron-beam emitting display device of the present invention is equipped with the glass spacers.
It should be noted that the xe2x80x9clinear expansion coefficientxe2x80x9d refers to the average value thereof at temperatures from 30xc2x0 C. to 400xc2x0 C.